This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Testosterone has emerged as a biological marker of personality (Sellers, Mehl &Josephs, 2007), motivating people to strive for dominance when status is uncertain. Despite documenting these effects in both sexes (e.g., Josephs et al., 2006), some have argued that estradiol is a better predictor of dominance in women (Stanton &Schultheiss, 2007;2009). Nonetheless, very little is known about the behavioral correlates of estradiol. New research points to an association between this hormone and implicit concern with relationships. As estradiol is a hormonal corollary of testosterone, it is reasonable to assume that following a competitive interaction, individuals might then be motivated to focus on maintaining relationships in an attempt to bring stability back to the social group. The experiment outlined in this pilot proposal is designed to explore this possibility. Participants will provide salivary samples to be assayed for testosterone and estradiol. They will then compete in same-sex dyads on a rigged-competition. Their behavior will be recorded and coded for dominant and affiliative behavior. I predict that changes in estradiol will be associated with affiliative behaviors and that testosterone will predict dominant behaviors.